This invention is directed to improvements in high voltage disconnect plugs of the type used to couple a television receiver's high voltage to the receiver's cathode ray tube.
Television projection systems typically include a television receiver, three CRTs (cathode ray tubes), and a screen on which the images developed by the CRTs are projected. High voltage for the CRTs is usually developed in the receiver and coupled to the CRTs via three separate high voltage plugs.
Referring to FIG. 1, a typical plug 10 is shown for coupling high voltage carried by an insulated wire 12 to a single CRT. The illustrated plug includes a lock nut 14, an annular rubber seal 16, a hollow spacer 18, and a sleeve 20. The end of the wire 12 includes a metal crimp 22 which makes contact with an inner conducter in the wire 12.
When the plug 10 is assembled, the sleeve 20 fits over the spacer 18 so that its end 24 engages and locks with the lock nut 14. In this condition, it is intended that the crimp 22 contact a screw 26 which protrudes into the sleeve 20, and that the seal 16 be tightly captured by the inner surface of the sleeve 20 where the sleeve engages the lock nut.
The plug 10 has been found to have several disadvantages. Specifically, the contact pressure between the crimp 22 and the screw 26 depends on how tightly the sleeve locks with the lock nut 14. The effectiveness of the seal 16 also depends on how tightly the lock nut holds the sleeve 20. If manufacturing tolerances are not fairly rigid, the sleeve 20 may be only loosely held by the lock nut 14, thereby allowing the crimp 22 to come out of contact with the screw 26. In addition, the possibility is increased of a high voltage arc jumping between the crimp 22 and a portion of the uncovered part of the wire 12 which may contact chassis ground. The latter problem is due at least partly to the failure of the sleeve 20 to tightly engage the seal 16, thereby providing a path for a high voltage arc. These problems also arise when the plug is subject to ambient temperatures which cause the lock nut and/or the sleeve 20 to expand or deform. For these reasons, high voltage plugs of this type are generally unsatisfactory.